The hydraulic system of a blood treatment device, for example a dialysis machine, has to be filled with fluid, for example an NaCl solution, before being connected up to a patient, in such a way that air pockets in the system that would be dangerous for a patient connected up to the fluids of the system are eliminated. Furthermore, the hydraulic system can be flushed with the filled-in fluid for a certain period of time in order to filter/wash out any contaminants, dirt particles, etc. that may have deposited in the system before the system is connected up to the patient. On an extracorporeal blood treatment device, these two procedures are performed in the scope of a filling-recirculation cycle.
In the state of the art, there are fluid containers, preferably in the shape of plastic bags, that are specially designed for extracorporeal blood treatment devices of this relevant type in order to enable, among others, the device functions as defined above. This kind of fluid containers is also manufactured and sold by the applicant filing the application in hand.
As a rule, such a fluid container has a fluid intake chamber and two preferably closable fluid connectors. On a first of the two connectors, an arterial line section, and on the second connector, a venous line section of the hydraulic system (fluid system) of the extracorporeal blood treatment device can be connected. The fluid bag as well as the two line sections together constitute a recirculation device of the extracorporeal blood treatment device.
For the fluid system filling process, first the arterial line section is connected to the first fluid connector of the bag, and after opening of the first fluid connector, the hydraulic system is filled. The venous line section of the system first remains open to the atmosphere (or is connected to a drain) so that air inside the system can escape/be vented in the atmosphere. As soon as the filling process is completed, the venous line section is connected to the second fluid connector of the bag in order to recirculate the fluid inside the hydraulic system of the extracorporeal blood treatment device for a certain period of time or a certain volume of flow through the bag chamber then.
During this recirculation process, the fluid flows through internal system filter devices in which possibly present contaminations and/or remaining air pockets are removed/filtered out with the fluid, which arise, for example, during the manufacturing of the system components such as hoses, valves, etc., and can get deposited in the system. Finally the venous line section of the hydraulic system is again disconnected from the second fluid connector of the fluid bag and the fluid contained in the hydraulic system is once again flushed out under constant supply of fluid from the container.
Upon termination of the recirculation process, the filling/recirculation cycle preparing for patient treatment is completed so that the two line sections (venous and arterial) can be disconnected from the fluid bag and connected up to the patient for treatment.
The description above of the filling/recirculation cycle of a hydraulic system/fluid conducting system of an extracorporeal blood treatment device (dialysis machine) known from the state of the art indicates that the fluid bag remains in the system circuit for the filling and recirculation processes, i.e. that the fluid inside the system is circulated through the fluid bag and/or its fluid chamber and consequently contaminates the fluid inside the fluid bag on a regular basis. The consequence of this is that with each new treatment preparation of the extracorporeal blood treatment device, a new fluid bag with fresh, uncontaminated fluid has to be used for the following filling/recirculation cycle, whereas the fluid bag for the filling/recirculation cycle performed before is disposed of independently of its residual content. It is obvious that this procedure results in the wasting of a large quantity of fluid in case of a high patient treatment number because the fluid content of a fluid bag can only be used (incompletely) for one filling/recirculation cycle.